I'm using Keras with the Theano backend on Ubuntu 16.04. My setup has been working without issues, however, all of a sudden I get the following error when I import Keras (import keras):
ValueError: You are trying to use the old GPU back-end. It was removed from Theano. Use device=cuda* now. See https://github.com/Theano/Theano/wiki/Converting-to-the-new-gpu-back-end%28gpuarray%29 for more information.
How do I resolve this?
You should change (or add) your environmental variable called THEANO_FLAGS. If you set the variable so that it contains device=cuda instead of device=gpu the error will be gone.
Also set the floating point precision to float32 when working on the GPU as that is usually much faster (THEANO_FLAGS='device=cuda,floatX=float32').